<%@ page language="java" pageEncoding="UTF-8"%>
<%@ page contentType="image/jpeg" import = "javax.imageio.*,java.util.*,java.awt.image.*,java.awt.*" %>
<%!

    //在此处 获取并生成随机颜色
    Color getRandColor(Random random, int ff, int cc) {

       if (ff > 255)
           ff = 255;
       if (cc > 255)
           cc = 255;
       int r = ff + random.nextInt(cc - ff);
       int g = ff + random.nextInt(cc - ff);
       int b = ff + random.nextInt(cc - ff);
       return new Color(r, g, b);
    }
%><%
	int randLen = 4;

    //在此处 设置JSP页面无缓存
    response.setHeader( "Pragma" , "No-cache" );
    response.setHeader( "Cache-Control" , "no-cache" );
    response.setDateHeader( "Expires" , 0);

    // 设置图片的长宽
    int width = 120;
    int height = 30;

    //设定被随机选取的中文字，此处中文字内容过多，不一一列出，只是举例说明下。
    String base = "\u9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f\u51c6\u97f3\u7b54\u54e5\u9645\u65e7\u795e\u5ea7\u7ae0\u538b\u6162\u53d4\u80cc\u7ec6" ;

    //设置 备选随机汉字的个数
    int length = base.length();

    // 创建缓存图像
    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

    // 获取图像
    Graphics g = image.getGraphics();

    // 创建随机函数的实例
    Random random = new Random();

    //此处 设定图像背景色
    g.setColor(getRandColor(random, 188, 235));
    g.fillRect(0, 0, width, height);

    //设置随机 备选的字体类型
    String[] fontTypes = { "\u5b8b\u4f53" , "\u65b0\u5b8b\u4f53" , "\u9ed1\u4f53" , "\u6977\u4f53" , "\u96b6\u4e66" };

    int fontTypesLength = fontTypes.length;

    // 在图片背景上增加噪点，增加图片分析难度

    g.setColor(getRandColor(random, 180, 199));
    g.setFont( new Font( "\u5b8b\u4f53", Font.PLAIN, 14));
    for ( int i = 0; i < randLen; i++) {
       g.drawString( "@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*@#*" ,0, 5 * (i + 2));
    }

    // 取随机产生的验证码 (4 个汉字 )
    // 保存生成的汉字字符串
    String sRand = "" ;
    for ( int i = 0; i < randLen; i++) {

       int start = random.nextInt(length);
       String rand = base.substring(start, start + 1);
       sRand += rand;
       // 设置图片上字体的颜色
       g.setColor(getRandColor(random, 10, 150));
       // 设置字体格式
       g.setFont( new Font(fontTypes[random.nextInt(fontTypesLength)],Font.BOLD, 12 + random.nextInt(6)));
       // 将此汉字画到验证图片上面
       g.drawString(rand, 30 * i + + random.nextInt(8), 24);
    }

    // 将验证码存入Session中
    session.setAttribute("randCode" , sRand);
    g.dispose();
    //将 图象输出到JSP页面中
    ImageIO.write(image, "JPEG" , response.getOutputStream());

    //关闭流

    out.clear();

    out=pageContext.pushBody();  

%>